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From: fkittred@bbn.com (Fletcher Kittredge)
Newsgroups: comp.sys.hp
Subject: Re: Strange behaviour on HP9000/825
Keywords: errno 25 cc errors
Message-ID: <43305@bbn.COM>
Date: 26 Jul 89 12:17:57 GMT
References: <227@innovus.UUCP>
Sender: news@bbn.COM
Reply-To: fkittred@BBN.COM (Fletcher Kittredge)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 34

In article <227@innovus.UUCP> martin@innovus.UUCP (Martin Renters) writes:
>
>We just found some rather strange behaviour on our 9000/825 running
>HP-UX 3.0.  Seems we get an errno 25 (not a typewriter) on the first
>I/O we do on any newly opened file, although the I/O is actually carried
>out. Any subsequent I/Os work fine, without error. Both HFS and NFS
>filesystems seem to have this problem.

>File opens, errno=0, fp=1073742056
>File read, errno=25, fp=1073742056, buffer=#include <stdio.h>
>File read2, errno=0, fp=1073742056, buffer=#include <errno.h>
>
>Anybody care to comment about why this is happening?
>

Sure, I'll comment.  I think you have a fundamental misunderstanding of
errno.  It is only guaranteed to be set to a meaningfull value after a
system call fails.  Since you don't check to see if a system call fails,
basically what your code is doing is checking the value of an uninitialized
variable.  As one might expect, you get garbage.

I recommend the following books:

"The Unix Programming Environment"
Kernighan and Pike
Prentice-Hall, 1984

"Advanced Unix Programming"
Rochkind
Prentice-Hall, 1985

regards,
fletcher
Fletcher E. Kittredge  fkittred@bbn.com